It probably sounds a bit crazy, but I think instruments would be modelled quite well as entities. Some of the problems instruments currently have:

They have multiple names. These can be variants in the same language (double bass = contrabass = acoustic upright bass), variants between countries (descant recorder = soprano recorder) or variants in different languages (recorder = Blockflöte). All these could be handled as aliases (with locales as appropriate). (see MBS-1028 too)

The names aren't unique (e.g. "tar" is the name of both a lute and a drum). These could be handled using disambiguation comments.

There are other sites with information about instruments, such as Wikipedia. We could use instrument-URL relationships to link to these.

Instruments (as credited in liner notes) do not form a nice tree (e.g. fue in Japanese refers to a variety of different Japanese flutes so doesn't fit nicely anywhere). Instead of a tree, we could use relationships to link to parent/child instruments. Then "shinobue" could be a child of both transverse flutes and fue, "shakuhachi" could be a child of both end-blown flutes and fue.

People can't easily edit descriptions, only relationship editors can do that. Annotations would let more people write instrument descriptions.

It's not possible to find out which artists/releases/recordings are using an instrument without directly searching the database. The entity page would display this information, like labels display releases from that label.

This would probably require 3-point relationships (MBS-1159)